This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Illegal copies of video content such as films may be produced in several ways.
A first example relevant to this invention is the making of copies in the movie theatre, usually with the aid of a smuggled video camera during a public screening of the film, but sometimes with the aid of the projectionist. Such copies are often spread over the Internet or on DVDs or other supports within days of the premier of the film, thereby causing important loss of revenue to the cinematographic industry, both for sales of cinema tickets and sales of DVDs.
In order to combat such copies, the prior art proposes the use of a so-called “Coded Anti-Piracy Code” (CAP Code) that burns each reel of film or batch of reels with a unique, visible mark that identifies the particular copy and, indirectly, the cinema theatre in which the film was screened. A drawback of the CAP Code system is that the marks are clearly visible to the audience and that they for this reason are introduced in a limited number of frames only so as to try and limit the disturbance. The result is that spectators sometimes complain nonetheless, while the pirates relatively easily may remove the code by suppressing a few frames.
A second example relevant to this invention, is the making of copies from a limited distribution DVD, such as a “screener DVD” distributed to film critics and jury members of film competitions such as the “Academy Awards®”. In this case, it is possible that the film has not even had its premier yet, and even graver loss of revenue and prestige may result.
A solution is, in this example as well, the insertion of a unique mark that identifies the person or the institution to which the DVD has been sent. A difference is that these marks may be clearly visible and that they may remind the viewer that no copy should be made and that the viewer can be identified if a copy is made nevertheless. A disadvantage is that these quite visible marks may have a negative impact of the viewer's appreciation of the film. Naturally, if such marks are inserted before the film starts, then they may very easily be removed by a pirate.
It can therefore be appreciated that there is a need for a solution that allows robust marking of video content so that the content may be uniquely identified, while the visual disturbance to the viewer is minimized or, if viewer disturbance is not a major concern, an alternative solution to the marking problem. This invention provides such a solution.